• Authors:
    • Kutcher, H. R.
    • Kryzanowski, L. M.
  • Source: Recent Trends in Soil Science and Agronomy Research in the Northern Great Plains of North America
  • Year: 2010
  • Summary: Variability in soil and crop productivity in the Northern Great Plains is related to the pedogenic development of the parent glacial deposits, climate, native vegetation, and topography. Anthropogenic field management over the past 100 years has contributed to additional field variability through tillage erosion, crop-fallow rotations, fertilizer management, livestock manure management and crop residue management. Field topography influences microclimate and the hydrological conditions within a landscape by the redistribution of water and soil thermal dynamics. Water movement from upper to lower slope and depression areas either by runoff or through subsoil will result in the physical redistribution of surface soil (erosion), translocation of soluble nutrients or accumulation of salts. The end result of this redistribution is drier warmer upper slopes, and wetter cooler lower slopes and depressions. This influences soil biological, chemical and physical processes that impact crop growth. Often, the lowest crop yields are measured on the upper slopes and the highest yields on the lower slopes. Upper slopes are prone to erosion, shallow surface horizons, higher carbonate levels, lower organic matter levels and lower available water. The lower slopes have deposits of eroded surface material, deeper surface horizons, greater depth to carbonates, higher organic matter levels and higher available water. However, spatial relationships between productivity and landscape position are not always consistent. Higher productivity does not always occur in lower slopes because yield reductions can occur as a result of planting delays, poor crop germination, poor soil aeration, poor drainage, poor root development, foliar and root diseases, compaction, nutrient deficiencies, weed competition, limited root development, stunted crop development, acidic soil and salinity. Precision farming provides an opportunity to utilize technology to manage the topographical and spatial variability. Elevation and positioning data collected from global positioning systems can be managed by means of geographic information systems. Landform segmentation provides a fundamental basis for subdividing fields into landscape management units based on topography. Field sensors such as crop yield monitors along with remote sensing, aerial photography, soil sampling and weed populations provide additional data layers needed for site specific management. Variable rate controllers provide the technology for fertilizer, manure, lime and herbicide applications. Ultimately, economics will determine the adoption of precision farming technology and practices.
  • Authors:
    • Paré, D.
    • Angers, D. A.
    • Laganière, J.
  • Source: Global Change Biology
  • Volume: 16
  • Issue: 1
  • Year: 2010
  • Summary: Deforestation usually results in significant losses of soil organic carbon (SOC). The rate and factors determining the recovery of this C pool with afforestation are still poorly understood. This paper provides a review of the influence of afforestation on SOC stocks based on a meta-analysis of 33 recent publications (totaling 120 sites and 189 observations), with the aim of determining the factors responsible for the restoration of SOC following afforestation. Based on a mixed linear model, the meta-analysis indicates that the main factors that contribute to restoring SOC stocks after afforestation are: previous land use, tree species planted, soil clay content, preplanting disturbance and, to a lesser extent, climatic zone. Specifically, this meta-analysis (1) indicates that the positive impact of afforestation on SOC stocks is more pronounced in cropland soils than in pastures or natural grasslands; (2) suggests that broadleaf tree species have a greater capacity to accumulate SOC than coniferous species; (3) underscores that afforestation using pine species does not result in a net loss of the whole soil-profile carbon stocks compared with initial values (agricultural soil) when the surface organic layer is included in the accounting; (4) demonstrates that clay-rich soils (>33%) have a greater capacity to accumulate SOC than soils with a lower clay content (<33%); (5) indicates that minimizing preplanting disturbances may increase the rate at which SOC stocks are replenished; and (6) suggests that afforestation carried out in the boreal climate zone results in small SOC losses compared with other climate zones, probably because trees grow more slowly under these conditions, although this does not rule out gains over time after the conversion. This study also highlights the importance of the methodological approach used when developing the sampling design, especially the inclusion of the organic layer in the accounting.
  • Authors:
    • Phillips, R. L.
    • Kronberg, S. L.
    • Gross, J. R.
    • Liebig, M. A.
  • Source: Journal of Environmental Quality
  • Volume: 39
  • Issue: 3
  • Year: 2010
  • Summary: The role of grassland ecosystems as net sinks or sources of greenhouse gases (GHGs) is limited by a paucity of information regarding management impacts on the flux of nitrous oxide (N2O) and methane (CH4). Furthermore, no long-term evaluation of net global warming potential (GWP) for grassland ecosystems in the northern Great Plains (NGP) of North America has been reported. Given this need, we sought to determine net GWP for three grazing management systems located within the NGP. Grazing management systems included two native vegetation pastures (moderately grazed pasture [MGP], heavily grazed pasture [HGP]) and a heavily grazed crested wheatgrass [Agropyron desertorum (Fisch. ex. Link) Schult.] pasture (CWP) near Mandan, ND. Factors evaluated for their contribution to GWP included (i) CO2 emissions associated with N fertilizer production and application, (ii) literature-derived estimates of CH4 production for enteric fermentation, (iii) change in soil organic carbon (SOC) over 44 yr using archived soil samples, and (iv) soil-atmosphere N2O and CH4 fluxes over 3 yr using static chamber methodology. Analysis of SOC indicated all pastures to be significant sinks for SOC, with sequestration rates ranging from 0.39 to 0.46 Mg C ha-1 yr-1. All pastures were minor sinks for CH4 (<2.0 kg CH4-C ha-1 yr-1). Greater N inputs within CWP contributed to annual N2O emission nearly threefold greater than HGP and MGP. Due to differences in stocking rate, CH4 production from enteric fermentation was nearly threefold less in MGP than CWP and HGP. When factors contributing to net GWP were summed, HGP and MGP were found to serve as net CO2equiv. sinks, while CWP was a net CO2equiv. source. Values for GWP and GHG intensity, however, indicated net reductions in GHG emissions can be most effectively achieved through moderate stocking rates on native vegetation in the NGP.
  • Authors:
    • Gross, J. R.
    • Tanaka, D. L.
    • Liebig, M. A.
  • Source: Soil Science Society of America Journal
  • Volume: 74
  • Issue: 2
  • Year: 2010
  • Summary: The inclusion of cover crops during fallow (i.e., green fallow) may mitigate greenhouse gas (GHG) emissions from dryland cropping systems. An investigation was conducted to quantify the effects of chemical and green fallow on soil organic C (SOC) and CO2, CH4, and N2O flux within spring wheat (Triticum aestivum L.)-fallow (chemical fallow) and spring wheat-safflower (Carthamus tinctorius L.)-rye (Secale cereale L.) (green fallow) under no-till management in west-central North Dakota. Using static chamber methodology, flux measurements were made during 19 mo of the fallow period of each cropping system. Soil samples collected before initiation of flux measurements indicated no difference in SOC in the surface 10 cm between cropping systems. Additionally, differences in gas flux between cropping systems were few. Emission of CO2 was greater under green fallow than chemical fallow during spring thaw until the termination of rye (P = 0.0071). Uptake of atmospheric CH4 was the dominant exchange process during the evaluation period, and was significantly (P = 0.0124) greater under chemical fallow (-2.7 g CH4-C ha-1 d-1) than green fallow (-1.5 g CH4-C ha-1 d-1) following the termination of rye. Cumulative fluxes of CO2, CH4, and N2O did not differ between the chemical- and green-fallow phases during the 19-mo period (P = 0.1293, 0.2629, and 0.9979, respectively). The results from this evaluation suggest there was no net GHG benefit from incorporating a rye cover crop during the fallow phase of a dryland cropping system under no-till management.
  • Authors:
    • Yang, Z.
    • Chen, D.
    • Li, M.
    • Liang, W.
    • Wang, K.
    • Wang, Y.
    • Han, S.
    • Zhou, Z.
    • Zheng, X.
    • Liu, C.
  • Source: Plant and Soil
  • Volume: 332
  • Issue: 1-2
  • Year: 2010
  • Summary: Cotton is one of the major crops worldwide and delivers fibers to textile industries across the globe. Its cultivation requires high nitrogen (N) input and additionally irrigation, and the combination of both has the potential to trigger high emissions of nitrous oxide (N2O) and nitric oxide (NO), thereby contributing to rising levels of greenhouse gases in the atmosphere. Using an automated static chamber measuring system, we monitored in high temporal resolution N2O and NO fluxes in an irrigated cotton field in Northern China, between January 1st and December 31st 2008. Mean daily fluxes varied between 5.8 to 373.0 µg N2O-N m-2 h-1 and -3.7 to 135.7 µg NO-N m-2 h-1, corresponding to an annual emission of 2.6 and 0.8 kg N ha-1 yr-1 for N2O and NO, respectively. The highest emissions of both gases were observed directly after the N fertilization and lasted approximately 1 month. During this time period, the emission was 0.85 and 0.22 kg N ha-1 for N2O and NO, respectively, and was responsible for 32.3% and 29.0% of the annual total N2O and NO loss. Soil temperature, moisture and mineral N content significantly affected the emissions of both gases (p<0.01). Direct emission factors were estimated to be 0.95% (N2O) and 0.24% (NO). We also analyzed the effects of sampling time and frequency on the estimations of annual cumulative N2O and NO emissions and found that low frequency measurements produced annual estimates which differed widely from those that were based on continuous measurements.
  • Authors:
    • Sun, O. J.
    • Wang, E.
    • Luo, Z.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 139
  • Issue: 1-2
  • Year: 2010
  • Summary: Adopting no-tillage in agro-ecosystems has been widely recommended as a means of enhancing carbon (C) sequestration in soils. However, study results are inconsistent and varying from significant increase to significant decrease. It is unclear whether this variability is caused by environmental, or management factors or by sampling errors and analysis methodology. Using meta-analysis, we assessed the response of soil organic carbon (SOC) to conversion of management practice from conventional tillage (CT) to no-tillage (NT) based on global data from 69 paired-experiments, where soil sampling extended deeper than 40 cm. We found that cultivation of natural soils for more than 5 years, on average, resulted in soil C loss of more than 20 t ha-1, with no significant difference between CT and NT. Conversion from CT to NT changed distribution of C in the soil profile significantly, but did not increase the total SOC except in double cropping systems. After adopting NT, soil C increased by 3.15 +- 2.42 t ha-1 (mean ± 95% confidence interval) in the surface 10 cm of soil, but declined by 3.30 ± 1.61 t ha-1 in the 20-40 cm soil layer. Overall, adopting NT did not enhance soil total C stock down to 40 cm. Increased number of crop species in rotation resulted in less C accumulation in the surface soil and greater C loss in deeper layer. Increased crop frequency seemed to have the opposite effect and significantly increased soil C by 11% in the 0-60 cm soil. Neither mean annual temperature and mean annual rainfall nor nitrogen fertilization and duration of adopting NT affected the response of soil C stock to the adoption of NT. Our results highlight that the role of adopting NT in sequestrating C is greatly regulated by cropping systems. Increasing cropping frequency might be a more efficient strategy to sequester C in agro-ecosystems. More information on the effects of increasing crop species and frequency on soil C input and decomposition processes is needed to further our understanding on the potential ability of C sequestration in agricultural soils.
  • Authors:
    • Stewart, G.
    • Gregorich, E. G.
    • McLaughlin, N. B.
    • Morrison, M. J.
    • Deen, W.
    • Tremblay, N.
    • Wu, T. Y.
    • Ma, B. L.
  • Source: Global Change Biology
  • Volume: 16
  • Issue: 1
  • Year: 2010
  • Summary: Nitrogen fertilization is considered as an important source of atmospheric N2O emission. A seven site-year on-farm field experiment was conducted at Ottawa and Guelph, ON and Saint-Valentin, QC, Canada to characterize the affect of the amount and timing of N fertilizer on N2O emission in corn (Zea mays L.) production. Using the static chamber method, gas samples were collected for 28-days after preplant and 28-days after sidedress fertilization at the seven site-year, resulting in 14 monitoring periods. For both methods of fertilization, peak N2O flux and cumulative emission increased with the amount of N applied, with rates ranging from 30 to 900 mu g N m(-2) h(-1). Depending on N amount and time of application, cumulative emission varied from 0.05 to 2.42 kg N ha(-1), equivalent to 0.03% to 1.45% of the N fertilizer applied. Differences in N2O emission peaks among fertilizer treatments were clearly separated in 13 out of 14 monitoring periods. Total N2O emissions may have been underestimated compared with annual monitoring in 10 out of the 49 cases because the monitoring period ended before N2O efflux returned to the baseline level. The flux of N2O was negligible when soil mineral N in the 0-15 cm layer was 15 degrees C was likely the driving force responsible for the higher levels of N2O found for sidedress than preplant application methods. However, caution must be taken when interpreting these later results as preplant fertilization may have continuously stimulated N2O emissions after the 28-days monitoring period, especially in situations where N2O effluxes have not fallen back to their baseline levels. Increasing fertilizer rates from 90 to 150 kg N ha(-1) resulted in slight increases in yields, but doubled cumulative N2O emissions.
  • Authors:
    • MDEQ
    • Midwestern GHG Reduction Accord
  • Volume: 2010
  • Year: 2010
  • Summary: The Midwest Greenhouse Gas Reduction Accord (MGGRA) was a commitment by the governors of six Midwestern states and the premier of one Canadian province to reduce greenhouse gas (GHG) emissions through a regional cap-and-trade program and other complementary policy measures. The Accord was signed in November 2007 as a part of the Midwestern Governors Association Energy Security and Climate Change Summit. Though MGGRA has not been formally suspended, participating states are no longer pursuing it.
  • Authors:
    • Hoben, J. P.
    • Gehl, R. J.
    • Grace, P. R.
    • Robertson, G. P.
    • Millar, N.
  • Source: Mitigation and Adaptation Strategies for Global Change
  • Volume: 15
  • Issue: 2
  • Year: 2010
  • Summary: Nitrous oxide (N2O) is a major greenhouse gas (GHG) product of intensive agriculture. Fertilizer nitrogen (N) rate is the best single predictor of N2O emissions in row-crop agriculture in the US Midwest. We use this relationship to propose a transparent, scientifically robust protocol that can be utilized by developers of agricultural offset projects for generating fungible GHG emission reduction credits for the emerging US carbon cap and trade market. By coupling predicted N2O flux with the recently developed maximum return to N (MRTN) approach for determining economically profitable N input rates for optimized crop yield, we provide the basis for incentivizing N2O reductions without affecting yields. The protocol, if widely adopted, could reduce N2O from fertilized row-crop agriculture by more than 50%. Although other management and environmental factors can influence N2O emissions, fertilizer N rate can be viewed as a single unambiguous proxy--a transparent, tangible, and readily manageable commodity. Our protocol addresses baseline establishment, additionality, permanence, variability, and leakage, and provides for producers and other stakeholders the economic and environmental incentives necessary for adoption of agricultural N2O reduction offset projects.
  • Authors:
    • Del Grosso, S. J.
  • Source: Nature
  • Volume: 464
  • Issue: 7290
  • Year: 2010
  • Summary: Most emissions of nitrous oxide from semi-arid, temperate grasslands usually occur during the spring thaw. The effects that grazing has on plant litter and snow cover dramatically reduce these seasonal emissions.